1. Requirements for UPS front-end power supply system

The UPS can provide the load with high-quality power with high voltage stability, stable frequency, and low waveform distortion, and it can provide uninterrupted power supply when switching with the static bypass. But to do this, the quality of its preamp power supply cannot be ignored. When we design the front-end power supply system of the communication room, we should consider the following aspects:

(1) The power quality of the front-end power supply system should not be too bad, and the voltage and frequency should be stable within the normal range.

(2) The pre-stage power supply system should not have other frequently started loads, such as frequently used elevators, frequently turned on air conditioners, etc.

(3) The capacity of the alternator unit in the front-end power supply system should be appropriately enlarged.

2. Determination of UPS capacity

According to the load capacity and nature, choosing an appropriate UPS can not only ensure the power supply quality of the UPS, reduce the failure rate, but also save investment and improve economic benefits. Generally speaking, the determination of UPS capacity is mainly to meet the needs of the current load. At the same time, several factors should also be considered:

(1) The influence of load properties on UPS output power.

(2) The capacity of the UPS should not be too large compared to the load, so that it is too light-loaded.

(3) The UPS capacity should not be too small, so that it will be in a heavy-duty operating state for a long time.

(4) For the case where the area of the communication equipment room is large and the load is continuously expanded by stages, when configuring the UPS capacity in the early stage, the medium and long-term development trend should be properly considered, and the model that can be operated in parallel or multi-machine operation should be selected in the selection, so as to When increasing the load capacity in the medium and long term, expand its output capacity through UPS paralleling. Correspondingly, when configuring the UPS input and output power distribution panels, the input switches of multiple UPSs and the load shunt switches in the medium and long term should be reserved for future expansion.

3. Electrical isolation and grounding of power supply system

Generally speaking, differential mode noise and common mode noise often exist in the power grid, and these noises interfere with the normal operation of the computer to varying degrees. In addition, the offset of the neutral line potential will also affect the operation of the computer, so measures should be taken to reduce these effects when considering the UPS power supply scheme. For more important loads such as large computer networks, the power supply system should try to use a UPS power supply with a power frequency isolation transformer.

4. Correctly configure the UPS backup battery

In order to ensure that the UPS power supply can continue to supply power to the computer when the power grid fails, the configuration of the backup battery is important.

The selection of battery capacity should follow the following: that is, the battery must supply power to the inverter within the backup time, and under rated load, the voltage of the battery pack should not drop below the reduced voltage allowed by the inverter. When arranging the equipment in the computer room, the battery pack should be as close as possible to the UPS host, the length of the connection between the two should be shortened, and the cross-sectional area of the connection should be increased to reduce the self-inductance of the connection and the voltage drop of the line. The battery pack can be installed in a battery cabinet or in an open battery rack, the former is aesthetically pleasing. Clean and tidy, but it requires higher load-bearing on the floor. The latter can disperse load-bearing and has good heat dissipation, but it occupies a large area and is easy to accumulate dust, which brings inconvenience to maintenance.

5. Increase power supply through redundancy

In order to improve the UPS power supply, various UPS redundant connection methods can be used. Each method has advantages and disadvantages. When considering the solution, the appropriate mode should be selected according to the actual load situation.

Currently, there are roughly three redundant connection methods:

(1) Dual-machine master-slave hot backup.

Connect the output of UPS1 as a slave to the bypass input of another UPS2 as a master. During normal operation, UPS2 supplies power, and UPS1 is in backup. When UPS2 fails, the load is switched to UPS2 bypass, and UPS1 undertakes the load supply task.

(2) Power sharing and parallel backup.

The system runs two or more UPS inverter units in parallel. Normally, two (or more) inverters supply power to the load at the same time. When one of the inverters fails, the UPS will be separated from the system. The required load current will be re-supplied by the remaining inverters according to the new share.

(3) Parallel hot backup.

The system connects the battery pack input, the rectifier output and the inverter output of two UPSs in parallel, and shares the bypass. Normally, the two rectifiers supply power to the two inverters at the same time, and charge the two sets of batteries, and output through the inverter. The static switch selects one of the inverters to supply power to the load, and the two rectifiers and inverters serve as backup for each other. Only when the two inverters fail at the same time, the system will switch the load to the common static bypass, and the mains will continue supply power to the load.

6. The power supply system should be intelligent

In order to ensure the long-term uninterrupted operation of the power supply system, the UPS is intelligent, which automatically detects the status of the UPS in operation and detects the failure of the UPS in time. Diagnosis and treatment, and reduce the interruption caused by failure or maintenance. At the same time, as a part of the power system of the communication room, a communication protocol should be provided so as to be included in the power centralized monitoring network.